3D printing a rocket engine

Most any rocket engine you’d find on a spacecraft – save for solid or hybrid rockets – use an engine system that’s fairly complex. Because of the intense heat, the fuel is circulated around the chamber before ignition giving a motor its regeneratively cooled nomenclature. This arrangement leads to a few complicated welding and machining processes, but surprisingly these obstacles can be overcome by simply printing a rocket engine on a 3D printer.

The current engine is quite small, but still fueled just like any other proper rocket engine that makes it into Earth orbit. The fuel is propane, the oxidizer is NO2, and the entire device is ignited with an automotive spark plug. Of course this was an expensive proposition; a motor with 12 pounds of thrust cost somewhere in the range of four figures.

Printing a rocket engine has a few advantages over traditional manufacturing techniques. [Rocket Moonlighting] explains that traditional techniques (mills, lathes and other heavy equipment) are bound by labor, material, and time. The costs of printing a rocket engine are only bound by the volume of the finished piece, meaning the most expensive engine per unit of thrust is the one that will fit in your pocket; scaling up means more efficiency for less cost.

There are a few videos up after the break showing the engine in action at full throttle, a few start and restart tests, and a test that involved throttling the engine. It’s an extremely impressive piece of kit, and hopefully [Rocket Moonlighting] will release the CAD source so we can make our own.

EDIT: [RM] tells me his engine cost less than $2000 to make. If just 10 people wanted their own engine from a ‘group buy,’ the price would drop by more than half. If you’d like your own 3D printed rocket engine, you might do well to drop [Rocket Moonlighting] a line.

25 thoughts on “3D printing a rocket engine”

There is a lot of methods, the plastic they printed can contain fine grains of steel, when all printing is done. The plastic-steel grain piece is put into an over, and the plastic is melt off, and the grains of steel is sintered/stick together.

or They may not have print the engine directly in stainless steel, they can printed a plastic replica, and used that to form the female model for casting.

At first I thought this would be another plastic one time use machine, like we’ve seen in the past few weeks (acrylic rocket engine, 3D printed gun, etc.) but the DMLS makes it far more viable as a real rocket engine replacement.

I’d love to see a sintering rig big enough to build NASA-scale rockets.

I’ve seen a setup with what looked like a 5-axis CNC machine with a MIG welder instead of a cutting head. It would start with a substrate, and build up a complex 3D shape over that, and it could go back over it with a cutting head to finish the part and refine the tolerances (if needed). SLS is probably a better way to go for a variety of reasons, but please feel free to prove me wrong.

I’ve heard a couple variations on the sintering. My favourite is probably electron beam sintering. Same concept, but you need a vacuum chamber instead of just inert gas. Also, it can produce hard xrays.

On the other hand, you don’t need a big ass laser and precision optics. Just a decent electron source and focusing magnets.

Call me silly, but everyone is talking about different forms of sintering etc to build this thing. Wouldn’t it be feesable for a home user to print it on a reprap or something and then cast it out of a strong metal for example: http://hackaday.com/2012/09/25/turning-3d-prints-into-aluminum-castings/ (ofc I think something with a higher melting point than alu, but I digress..)

Nope. The problem is that metal casting is very finicky around internal shapes, and the smaller the part the worse it gets. The metal will adhere to walls, surface tension or bubbles will block flow, or the metal cools too fast and stops.

DMLS and E-beam sintering can do things that just are not possible with casting.

John: I am the one that did the castings on the link Rambo provided. Internal shapes are no more difficult than exterior shapes. The only issue is with extremely small or thin (less than 1-2mm) sections with gravity castings. That said, small parts are routinely cast with centrifugal casting; that is how practically all jewelry is cast. Very small parts with insane level of detail can in fact be cast with centrifugal casting.

Jakob: Being charitable, I’d guess this is an extremely clunky way of saying “it gets to be called regeneratively cooled because it circulates the fuel”. Ditto nomenclature is really not the best word but as a sentence it kind of makes sense if you squint just right.

Sometimes I wonder if HaD’s editing is kept deliberately bad as an in-joke at this stage.

The $/watt cost of lasers has come down significantly. A 40w off the shelf laser tube will run you about $400. There was a HaD post about a fellow that is building his own “hardware store” lasers for around $75 at an estimated 25w. With some refinement I immagine he could achieve an inexpensive 50w tube.

Would it be possible to use an array of lasers and a prisim based beam combiner to achieve 200+ watts?